1. Field of the Invention
This invention generally relates to an apparatus and a process for monitoring and/or providing a quantitative and/or qualitative indication of insect infestations in stored products.
2. Description of the Related Art
Protection of stored agricultural commodities from insect infestations and the direct loss caused by insects are costly. Insect infestations in stored agricultural commodities result in annual losses of millions of dollars. Early detection of infestation problems is necessary to initiate timely control measures and eliminate unnecessary “scheduled” insect treatments. Routine use of insecticides to protect stored products may have constraints.
The standard practice for detecting and quantifying infestation in stored grain is visual inspection of samples for adult insects. Insects are usually separated from grain samples with hand or inclined sieves. A traditional method of obtaining samples uses a long, hollow multi-compartment grain trier inserted into the commodity. Its gates are then opened and closed to acquire samples at different depths and, after withdrawal, the samples are removed for inspection (Bauwin et al., In: Storage of Cereal Grains and Their Products; 2nd edition, ED: C. M. Christensen, 115-157, 1974; St. Paul, Minn.:American Association of Cereal Chemists). Other methods can get beyond the limitation of only sampling close to the grain's surface. A vacuum probe can extract larger samples from deeper with a grain mass and a grain mass can be turned enabling a pelican sampler to catch samples from the moving grain stream (Noyes et al., In: Management of Grain, Bulk Commodities, and Bagged Products, Circular E-912, 71-79, Cooperative Extension Service, Oklahoma State University, 1991). None of these sampling techniques provide continuous and thorough monitoring. Low insect populations are difficult to detect in small samples and a much greater proportion of the grain needs to be sampled to accurately estimate insect population size (Hagstrum et al., IN: Management of Grain, Bulk Commodities, and Bagged Products, Circular E-912, 65-69, Cooperative Extension Service, Oklahoma State University, 1991). Additionally, theses sampling methods are expensive and labor intensive and therefore not repeated very often even though an infestation can grow from undetectable to damaging levels in two weeks. Another method, employed in some large grain elevators, is temperature sensing cables distributed throughout the storage volume. This system is only sensitive to very high insect populations. Furthermore, both moisture and mold growth can elevate temperature levels.
White et al., (Journal of the Kansas Entomological Society, Volume 63(4), 506-525, 1990) and Reed et al. (Journal of Economic Entomology, Volume 84(4), 1381-1387, 1991) both disclose passive grain probe traps that have been developed. The probes are vertical perforated tubes that insects crawl into and then drop through to be trapped in a reservoir at the lower end. Probes are left in the grain for prolonged periods, allowing them to continuously capture insects and thus detect very low insect populations. However, the information is only available after the labor intensive process of inserting the trap into the grain, waiting, withdrawing the trap, and then inspecting the trap contents. The difficulty of insertion and withdrawal increases with the distance from the surface due to the resistance of the grain.
U.S. Pat. No. 5,005,416 discloses an automated, continuous monitoring electronic grain probe trap with a bottom reservoir fitted with a detector that senses the movements of trapped insects. The number of insects caught in the trap is estimated based on the amount of vibration detected. However, temperature, species, time in the trap, the amount of food, and other insects in the trap are all factors which can affect the trapped insects' vibration producing activity. Vibration detection may also be prone to error from ambient noise.
Hagstrum et al. (Proceedings 6th International Working Conference on Stored-Product Protection, Canberra, Australia, Volume 1, 403-405, 1994) disclose a computer-based acoustic system that provides for automated monitoring by detecting insect generated sounds. Piezoelectric transducers, mounted on vertical cables installed in grain bins, sense the feeding and movement sounds of nearby insects. The acoustic sensor outputs are sequentially connected to electronic components that count and relay to a computer, the number of signal peaks crossing a threshold level during each sensor's observation interval.
U.S. Pat. No. 5,646,404 (herein incorporated by reference) discloses an electronic grain probe insect counter (EGPIC) which provides real-time monitoring of insects using infrared beam technology to detect insects as they fall through modified grain probe traps. When an insect falls through the trap, it partially masks an infrared beam. Whenever one of the traps infrared-beam sensor output signals exceeds a precise detector threshold level (this level being set to specify the minimum detectable insect size), the resulting quantitative insect detection or count is recorded and time-stamped to provide an ongoing indication of infestation levels in stored-products. The real-time data acquired by an EGPIC system are used to display the numbers of insects that have been counted within specific commodity regions and time periods. If the rate of insect counts are below a known threshold (based on factors such as economics, tolerance, environmental parameters, etc.), no control action is necessary. However, if the rate is above that threshold, the appropriate response may be a function of the species being counted. This is because the relationship between insect counts and population density is a function of species. Therefore, the appropriate first response may be to go into the commodity storage and identify the species at those probe sites that are getting the high insect counts. Then, with that species information, a decision can be made as to if and what control response is warranted. Thus, while the EGPIC system can eliminate the need to visually inspect the commodity on an ongoing scheduled basis, increasing insect counts may still mandate a visual inspection before control decisions are made. The EGPIC system employs a sensitivity control in order that it not count objects smaller than the smallest stored-product insect of concern (e.g., grain particles). Because of this, smaller insects such as psocids and mites are not counted even though their presence may be of interest to the facility manager. This sensitivity control must be set conservatively (higher sensitivity) in order to ensure that each probe maintains a reasonable count accuracy with the smallest stored-product insect of concern because of large electronic and mechanical component variability across probes. However, this may occasionally lead to false positives due to other very small insects (e.g., psocids) and grain particles. Other potential sources of false positives are electrical impulse noise (e.g., generated by electric machinery) and a crawling or clinging insect managing to get near the infrared beam which can cause a multitude of false counts. The EGPIC system has a self-test feature to insure that receiving no counts from a probe is not an indication of a probe or system failure. At regular time intervals, the system momentarily decreases the infrared beam source output, simulating an insect falling through and masking part of the beam, and then checks whether this “count” is detected. However, this is a pass/fail test, so there is no warning of a gradual performance degradation until failure occurs.
While various methods and systems have been developed for monitoring insect infestations in stored-products, there remains a need in the art for a system for remote monitoring of pest infestations which provides a more accurate count and species identification. The present invention provides a remote system for automatically counting insects which enables a qualitative analysis of an analog sensor output signal to provide additional information that can help identify species, reject erroneous counts, etc. which is different from prior art methods and systems.